Device for amplifying and diffusing sound



June 12, 1934. 'iM 1,9 62,300

DEVICE FOR AMPLIFYING AND DIFFUSING SOUND Filed Jan. 14, 1929 2 Sheets-Sheet 1 Fig .30

Fig .2.

INVENTOR Armand FrmM Ephraii'n BY fa ATTORNEYS June 12, 1934. F, EPHRA'I'M 1,962,300

DEVICE FOR AMPLIFYING AND DIFFUSING SOUND Filed Jan. 14, 1929 2 Sheets-Sheet 2 INVENTOR Armand Frmrxlfll'phrdihr ATTORNE Y5 Patented June 12, 1934 v UNITED STATES;

PATENT OFFICE Armand Fernand Ephraim, Paris, France App ication January 14, 1929, Serial No. 332,479 In France January 20, 128

5 Claims.

The present invention relates to apparatus such as loud speakers for wireless telephony, gramophones and other apparatus for reproducing musical sounds, and has for its ,purpose to render such apparatus clearer and agreeable to listen to.

Although manufacturers of loud speakers all affirm that their apparatus do not distort sounds, it must be acknowledged that a loud speaker or a diffuser, whatever it may be, is, properly speaking, none other than a musical instrument and possesses a characteristic tone the parasitic vibrations of which mingle with the vibrations of the sounds which are to be reproduced.

There is no vibration. without vibrating material and it is the reason why it cannot be expected to manufacture aloud speaker-or a diffuser which has not its own tone.

The efiect produced by the parasitic sonorities is comparable to the effect of a resonator.

Now, if it is not possible to completely eliminate the phenomenon of resonance, it is on the contrary possible to cause it to be disagreeable or not. It all depends on the choice ofthe resonator.

If a. singer sings before a saucepan, a caldron or an empty barrel, his voice takes an abnormal ';and very disagreeable tone.

-On the contrary if he sings in a drawing room, concert hall or a theater, his voice, although modified every time by the particular resonance of the premises, will always preserve an agreeable and natural tone. I

The present invention consists in taking as main amplifying element not a metallic horn,

a wooden 'box, a tabour or any other object of reduced dimensions, but an auditorium or a living room of several cubic meters.

' For that purpose, the rim of an electrodynamic or electromagnetic loud speaker is joined by means of tapered members to the walls of an auditorium, listening room or the like, whereby said walls become substantially extensions of .the walls of the loud speaker and -constitute together a closed resonator of great size by means of which the reproduced sounds are highly amplified without undesirable distortion. Then, said resonator having a capacity of several cubic meters, the parasitic sounds issuing from the same and mingling with the repro-' *duced sounds will be of the same nature as those which would naturally mingle with the human voice, if a singer would sing in the place and stead of the reproducing apparatus. Artistic auditions are thus obtained giving, if not the rigorous reproduction of the sounds emitted before the radiophonic microphone, at least quite a good imitation capable of giving the illusion of reality.

In addition to the quality of the tone, the present invention allows moreover of obtaining very interesting technical advantages.

When use is made of a loud speaker of a usual type, placed in the middle of a living room vor of an auditorium, there is a first beam or -bundle of sonorous waves emitted by the front face of the apparatus and a second beam or ,bundle, directed in the opposite direction, emitted by the rear face. These two beams or bundles by reflecting on the walls of the room, give rise to two reflected beams. These four .beams interfere together, and this causes for not disturbed byv interferences and'that, moreover,

the audition is quite as good, whatever may be the point of the room where the listener is placed, the distribution of the sound being uniform and without privileged direction.

The fact, for the listener, of being placed within the resonator has also another important advantage:

The 'listener completely surrounded by the sonorous waves, determines with great difliculties, his eyes being shut, the exact place or location of the source from which the sounds are emitted concerning the direction, and cannot determine at all the distance. The result is that the listener can'imagine a singer or-a violinist at a distance which corresponds to the intensity of the sound. Thus, when the invention is used in a listening room for talking pictures, 100 the listeners have a strong illusion that the words heard issue from the mouths of the characters projected on the screen. Furthermore, the sound is distributed uniformly throughout the entire room and patrons occupying seats 105 at all points therein are enabled to hear without diillculty and in uniform volume the reproduced sound. I By way of example the accompanying drawings show diagrammatically various 'modes of 110 carrying these arrangements into practice.

these drawings,

Figure 1 shows a perspective view of an arrangement of a loud speaker suspended in an angular space in such a manner that it directs the sound waves within the trihedron formed by two walls and a ceiling.

Figures 2, 3 and 4 show respectively a front view, a side view and a plan of the loud speaker horn of special shape shown in Fig. 1.

Figure 5 shows diagrammatically, in perspective, view, an upper corner of a locality in which the ceiling is provided with decorative cornices masking the upper edges of the diffusing trihedron.

Figures 6, 7 and 8 show, in elevation, profile and plan, respectively, a similar cone to that shown in Figure 1 but modified as to its mouth in order to adapt it to the shape of the cornice.

Figure 9 shows, on a plane bisecting the dihedron formed by the walls, a section of a simplified form of cone which can be utilized in the case of ceiling with cornices;

Fig. 10 shows a longitudinal diagrammatic section of an auditorium specially furnished according to the principle of the invention.

Figures 1 to 4 show an arrangement of loud speaker for wireless telephony which gives the best results (it being understood that the radiophonic emission is pure, that the receiving station does not deform it either at high or low frequencies and that the receiver is suitably chosen).

This arrangement comprises a conical tube,a mounted on the telephonic receiver b in the usual manner. This cone is preferably of a very elongated form and of a non-resonant material such as cardboard. It is better still to construct it of several superposed sheets of thick paper or of thin cardboard, the said sheets not being stuck together so as to form a single block, but forming on the contrary quite distinct layers. There is thus obtained a perfect damping of the walls of the cone which results in the elimination of parasitic vibrations.

The cone 0 is preferably formed with flattened faces a, Figure 4. forming a rectangular dihedron intended to fit exactly in the dihedron formed by the two right -angle walls m, m. It is formed at its upper part with an arched part or inclined surface a, Figure 3, intended to rest against the ceiling p, which without being indispensable has a very marked effect. It serves to modify the direction of the sound waves without disturbing them. It can be shown indeed that when this arch is omitted. the sounds reflected by the ceiling are returned and at times give place to vexatious interfer- A claw 4' allows the born a to be suspended nail n inserted in the angle of the two at the desired place. It is also satisfacmake a hole in the wall of the horn and it on the nail.

Usually in rooms the angles 0A and OH of the trihedron, Figure 5, are masked by a moulded cornice d which if it is not especially detrimental to the diffusion of the sound (by reason of the fact that its diffraction becomes so much the more of importance as the length of the wave is increased) renders difficult the placing of the horn in the best position to give the best results. For good results the arch and the mouth of the horn should be made to conform with the shape of the cornice in such a manner that it would fit closely thereto and the wall surfaces are in some degree extensions of those of the horn.

Figures 6, 7 and 8 show a form of horn which can be adapted in a satisfactory manner to the more usual form of cornice.

The conical horn a and its arch a are "truncated to provide inclined facets a. which permit the horn to be thrust upwardly until the apex of the arch a touches the ceiling.

It should be noticed that the front part of the horn a is formed with a tongue a which extends close to the ceiling and facilitates, in certain cases, the emission of sound by spreading the sound waves.

When the cornice is of large dimensions, as shown in Figure 9, the arch a can be omitted, the sound being sufiiciently deflected by the moulded surface so that there is no interference.

In this case the best results will be obtained with a cone of 2 metres to 2.50 metres in height and of to centimetres opening, and preferably provided with a sufficiently large tongue a at its upper front part.

In place of the trihedron formedby two walls and the ceiling, the trihedron formed by two walls and the floor can be employed to constitute an extension of the walls of the loud speaker. When the floor is thus used in place of the ceiling, the difliculties which result from the presence of a corniceand mouldings are avoided. It is however indispensable that the corner utilized for diffusion shall be unobstructed and all furniture should be removed from within a radius of at least two metres. The presence of a carpet is not so favourable and this is why the utilization of the ceiling is considered to be more usual.

In the preceding description it has been supposed that it is required to utilize 'the ordinary walls of an existing room without any modification. If it is proposed to construct a special room intended for performances (for example in order to enable a symphonic concert performed in the capital to be heard in a provincial town, or in order to enable the voice of a speaker or political orator to be heard by thou sands of listeners) the best results will be obtained by replacing the wall at the end of the room by a large hopper-like structure at the upper part of which the loud speaker could be pla byway of example, the dimensions, forms and detailed arrangements can be varied without departing from the principle of the invention.

I claim:-

1. A loudspeaker adapted to be located in a corner of three walls of a room, comprising a reflecting member adapted to fit substantially all round when in place, with all the walls of the corner, means being associated therewith for positioning said loudspeaker respectively to the walls of the corner, whereby, upon putting the loudspeaker in place any lateral discharge of the vibrating air-column, at the outlet of the loudspeaker, gets prevented by the besetting walls of the room.

2. i A loudspeaker provided with a horn having an outlet shapedaccording to the form or the walls and mouldings of a room, with rims adapted to fit, when in place, substantiallyall round with'besetting walls and mouldings, means being associated therewith for positioning said loudspeaker and horn respectively to the walls of the room, whereby upon putting the loudspeaker in place, any lateral discharge of the vibrating air-column, at the outlet of the loudspeaker, gets prevented by the besetting walls ofthe room.

3. A loudspeaker provided with a horn adapted to be located in the trihedron formed by two walls and the ceiling of a room, the flared outlet of said horn being adapted to fit substantially all round, when in place, with said walls and ceiling, means being associated therewith for positioning said loudspeaker respectively to the walls of the trihedron, whereby, upon putting the loudspeaker in place, any lateral discharge of the vibrating air-column, at the outlet of the loudspeaker, gets prevented by the besetting walls of the room.

4. In a loudspeaker, the combination with a sound producing apparatus of usual type, of a conical horn shaped to adapt it to be vertically suspended in the corner of a room, and of an arched member surmounting the flared orifice of the horn, and exactly fitting in the trihedron formed by the walls and the ceiling of a room, where the ceiling and walls of said trihedron constitute substantially extensions of the walls of the arched member.

5. In a loudspeaker, means for increasing the length of the vibrating air column, said 'means comprising an arched member shaped according t6 the form of a geometrical trihedron, with its outlines fitting with the three facesof said trihedron, a conical horn fitting with said arched member, and means for hanging said horn vertically in the corner of a listening room, with the arched member setting in the trihedron formed by the ceiling and two adjacent walls of the room, whereby, upon putting the loudspeaker in place, the walls of the room will constitute substantially an extension of the horn.

/ ARMANI) FERNAND EPHRAIM. 

